This invention relates to wireless local area networks (“LANs”), and more particularly, to wireless local area networks that carry a mixed traffic of voice and data.
Wireless LANs are typically used in applications that involve mobile computers, in applications where wireline installation is not feasible, etc. Such applications include warehouse inventory tracking, portable point of sale, shipping and receiving, package tracking, etc.
The IEEE 802.11 communications standard has been used by some vendors to provide interoperability between wireless LAN equipment. The 802.11 standard specifies a protocol in which information is transmitted in packets. The standard specifies features such as packet size, packet content information, data rates, roaming, etc. The primary type of information that was initially transmitted in systems that were designed to the 802.11 standard as published was information such as barcode information, point of sale information, package tracking information, etc. In such known systems, several remote terminals may be in communications with a single access point to receive and transmit information such as bar code information, point of sale information, package tracking information, etc. The standard as published specifies a communications medium that is shared by transmitters (e.g., an access point and one or more remote terminals).
The standard further specifies that packet size may vary. A remote terminal that has a relatively large packet to transmit may need to occupy the shared communications medium for a longer period than a remote terminal that has a relatively short packet to transmit. Until recently, delays in communicating packets have typically been non-critical to providing communications at least partly because of the type of information that has been transmitted in such systems. Information such as bar code information, package tracking information, etc. typically remains valid until a next incremental event occurs (e.g., until bar code information has changed, until a package is tracked to a next point in route, etc.). In addition, such information does not generally affect system communications if delivered with some delay.
In some known systems, packets are simply transmitted in the order in which they have been received for transmission. In these known systems, a packet that is transmitted without being properly acknowledged by its intended recipient is repeated for a predetermined number of times while transmission of other remaining packets is delayed. After retransmitting a packet for a predetermined number of times without receiving a proper acknowledgment, the transmitter may proceed to transmit the remaining packets.
The demand for providing mixed voice and data traffic in wireless LAN systems has been increasing over recent years. Currently, the 802.11 standard does not provide specifications for providing voice communications. Information for providing voice communications is generally much more time critical than other information such as bar code information, package tracking information, etc. Communications for providing voice communications may require a greater volume of information to be carried by the system than when the system is providing communications for information that has typically been carried by wireless LANs. Moreover, the quality of voice communications is dependent on the rate in which information is exchanged. In data communications such as in communications for package tracking, the rate in which information is exchanged is non-critical because the quality of such communications is typically not a factor in evaluating the effectiveness of such communications.
Some known wireless LANs carry voice signals as part of the communications traffic but these systems are deficient in effectively meeting such complex communications demands as discussed above. Moreover, there may be a need to meet such demands with existing systems without substantially increasing system complexity, structure, design, cost, etc.